Water tube boiler



17, 1935. o. ENGLER WATER TUBEBOILER Filed Nov. 30, 1932 ATTORNEY Patented Dec. 1 7, 1935 WATER 'run n BOILER Otto Engle'r, Cassel-Wilhelmshohe,

er to schmidtsc Germany, as-

he Heissdampt-Gesellschai't m. b. 11., Cassel-Wilhelmshohe, Germany Application November 30, 1932, Berial No. 544,967 Germany December 17, 1931 3 Claims. (01. 122-235) In water tube boilers having risers arranged in rows which are unequally heated, it is old to group risers and downcomers into several groups each having its own water circulation. If, as is frequently the case, risers receiving difierent amounts of heat belong to one and the same circulation group, there is danger that at certain loads only those rows of tubes which receive the larger amounts of heat will have a sufiicient water supply, while in the risers of the group which receivethe leastamount of heat the circulation of the water may be interrupted, and there may even be a reversal of the circulation, with its objectionable results. It is also old to associate with each single row of risers of a bank a row of down comers to form a circulation group. In such cases the arrangement is such that the row of risers which is swept by the hottest gases is grouped with the downcomers with which the gases. may contact last and which is therefore heated least, while in the nextfollowing groups the diiference in heating between the risers and the associated downcomers is progressively smaller so that the danger of interruptions in circulation increases correspondingly.

In order to avoid the disadvantages pointed out and to assurean ample water circulation in each of the differently heated riser groups, the risers and downcomers are according to the present invention so grouped that each circulation groupconsists'of groups of risers which are substantially equally-heated and have-approximately the same resistance to fiow through them, and of downcomers which lie in Zones of materially lower temperature than the risers of the respective group. Such an arrangement avoids having a circulation group include for example risers which receive their heat by radiation and are therefore very active and also risers which areheated only by convection. It further avoids having risers,

which are heated only by convection by. gases which are already very materially cooled, and

which therefore receive relatively small amounts I of heat, grouped with downcomers which are also heated'even if they lie behind such risers in the direction of gas fiow. The invention utilizes an arrangement that is admissible which is to group downcomers which are slightly heated with risers which receive a large amount of heat to forms. circulation group. In such an arrangement the difference in temperature between the risers and downcomers is large enough to ensure a definite circulation; I The grouping of risers and downcomers into circulation groups can be accomplished by means the bottom of the furnace.

1 but at their lower ends are connected to a separate lower drum 56.. The tubes of bank 5| also which are old by themselves. for instance by fiuid conducting means built into the lower-drum and forming return channels from the outlets of the downcomers to the inlets of the risers. The same thing may be accomplished, however, by having the tubes of each circulation group open into its own separate lower drum.

In the drawing, one illustrative example of the invention is shown, together with one variation.

Fig. 1 is a vertical section through a semi-ver- 1p tical tube boiler embodying the invention; Fig. 2 is a horizontal half-section on line 2-2 of Fig. 1. Fig. 3 is a fragmentary vertical section of a vari vation.

The boiler shown in Figs. 1 and 2 is a semi- 15 vertical tube boiler arranged for oil firing. The burners 44 are arranged in the front wall 42 of the furnace 43. Each lateral wall 45 of the furnace is provided with a water wall of evaporator tubes 46 connected'at their upper ends to thesteam and water drum 4! and at their lower ends to a drum 48. These water tubes have vertical portions adjacent and parallel to the water walls and horizontal portions parallel and adjacent to- Their 'ends lie in '25 single rows but obviously these ends might-be arranged in two or, more rows. The gases-issuing, 7

from the furnade 43 flow in sequence through the f y evaporating bankflil, a superheater 50 (indicated sage 52 containing an air preheater 53.

The evaporator bank 49 is subdivided into two groups. One of these consists of the two front rows 54 extending between the upper drum 4! and lower drun 48, and the second consists of the rear rows of tubes 55 which at their upper ends are also connected to the upper drum 41 are all connected to the upper drum 41, but are divided into two groups, namely, a front one 51 receiving more heat and connected to the lower drum 48, and a rear'group 58 receiving less heat and connected tothe lower drum 56. In this manner the water screen tubes 46 and the two front rows 54 of the evaporating bank 49 together with the group 51 form the first closed circulation group utilizing" the lower drum 48 to close the circuit, andthe rear rows of the bank 49 to- I gather with the group 58 form a second circula- I tion group through the lower drum 56. In the first circulation group the tubes 46 and 54 are risers and the tubes 51 are downcomers; The so tubes 46 are heated principally by radiation and the two rows 54 likewise receive radiant heat. The tubes 46 and 54 are therefore heated to approximately the same extent. As they also have approximately the same resistance to flow through them they may be connected into a single group. It will be understood that the tubes 46 are present in the form of boiler shown, as this is an oil-fired case. This type of boiler was chosen to illustrate that such tubes as 46 can be gathered into the same group "with the portion of the bank nearest the furnace. In many instances there will be no tubes like tubes 46. The downcomers 51 associated with the group comprising tubes 54 are heated by hot gases which have passed through the bank 49 and the superheater 50. The difierence in temperature between them and the risers of this circulation group is therefore suihcient to assure a reliable water circulation.v These conditions are also present in the second circulationgroup. The evaporating tubes 55 of this group acting as risers rare swept bythe hottest combustion gases, whereas in that zone where the downcomers of this group lie, the

heating gases have beenlargely cooled because in addition to thebank 49 and the superheater 60 they have also been in contact with the downcomer bank 61 of the first group.

In-the modified example of Fig. ,3 the two circulation groups do not utilize separate lower drums, but a common lower drum 60 is used for the two circulation groups. and the grouping of Q the tubes is eflected through appropriate strucis effected through the connecting pipes 65 and the connection between the boxes 62 and 64 of the second circulation group through the con-' necting pips.66. A suitable number of these connecting pipes is distributed throughout the length of the drum-60. The connecting pipes 65 bridge the box 62 lying between the boxes 6| and 66 and the connecting pipes 66 bridge the box 63 lying between the boxes 62 and 64. The boxes are preferably secured to the wall of the drum by some readily detachable means.

It will be obvious from the above that the invention may beapplied to boilers of semi-vertical water tube type other than the specific form shown.

For example, the circulation groups according to Figs. 1 and 3 could be used in a marine boiler of the A-type. By separating the groups oi riser 5 tubes which have varying degrees of heating and varying flow resistance into separate circulation .groups with downcomers that are heated only slightly as compared with their associated risers, a constant circulation through all the risers without any danger of stoppage or reversal is assured in each case. Furthermore a. proper relation between the cross-sectional area oi. the risers and downcomers of each group can be selected and the number of downcomers can be kept as small as admissible.

What I claim is: V

1. In a boiler, the combination 0! a plurality of groups of upright transversely alined riser tubes, means to cause hot gases to flow in a direction generally across the tubes so that the tubes in each transverse row receive substantially equal amounts 01' heat and successive groups receive progressively decreasing amounts of heat, all the tubes of any group oilering substantially the same resistance to the flow of fluid through them, upper and lower water containing means to which the tubes are connected, and downcomers connected with the risers to establish a plurality oi separate circulation systems, each circulation system including downcomers and one group of risers, the downcomers also being exposed to heating conditions but in each case to less intense heating conditions than any of the risers of the boiler, the downcomers of all the systems lying. with respect to the gas flow beyond all 01. the risers, and all the downcomers of one system lying, with respect to the gasilow, behind the downcomers of a second system whose risers receive more intense heat than those of the first system. I P 2. A boiler in accordance with claim 1, the lower ends 01' the downcomers 01' one system crossing the lower ends of the risers of another system. a 4

3. A boiler. in accordance with claim 1, the lower water containing means being a single drum, thelower ends of each group of risers and the lower ends of each group of downcomers being separately enclosed in boxes arranged in said lower drum, boxes pertaining to one system being connected by conduits bridging a box pertaining to another system.

, O'I'IO ENGLER. 

